The present invention is generally directed to carbon thin films, methods of their deposition, and methods of their use in Nanoelectromechanical Systems (NEMS), Microelectromechanical Systems (MEMS) and other devices. More particularly, the invention provides methods of carbon thin film deposition and methods of making carbon containing patterned structures. The invention also provides methods of controlling physical properties of carbon thin films. Moreover, the invention provides methods of use of carbon thin films and carbon containing patterned structures in devices. In particular, the invention provides use of carbon thin films as electrochemical sensors in a high performance liquid chromatography device.
Electronic systems interface with the real world through sensors and actuators. The technological development of sensors and actuators often relies on the production and characterization of new materials. MEMS and increasingly NEMS draw upon traditional semiconductor fabrication methods to produce novel minituarized sensors and actuators. NEMS and MEMS are often smaller, cheaper and more reliable than their traditional counterparts and sometimes open up new possibilities.
Various forms of carbon are used in many technological applications due to carbon's superior electrical, mechanical, thermal and chemical properties. It is highly desirable to utilize the unique properties of carbon in NEMS and MEMS as well. To introduce carbon into NEMS and MEMS, however, well controlled and well characterized methods of carbon thin film deposition are desired.
Carbons can be prepared by the pyrolysis of various carbonaceous precursors such as wood, coal, lignite. Polymers can also be used as precursors of pyrolyzed carbons. Recently, Ranganathan et. al. reported photoresist-derived carbon for MEMS and electrochemical applications (see, Ranganathan et al., J. Electrochemical Society, 147 (1), 277-282 (2000)).
Parylene can be an attractive candidate for pyrolysis because of its benzene-rich chemical structure. The use of parylene as the precursor of the pyrolyzed carbon in MEMS provides a new material for MEMS, while utilizing certain advantages of parylene based MEMS. Hui et. al. reported limited examples of carbon thin films prepared from pyrolyzed parylene. However, Hui et. al. did not study the details of parylene pyrolysis, their method of carbon thin film deposition was not optimized, and they did not report the electrical and mechanical properties of their carbon thin films. Consequently, the method by Hui et. al. is not characterized enough and is not controlled enough to be used for introduction of parylene-pyrolyzed carbon thin films into MEMS or NEMS.
The present invention provides well characterized and well controlled methods of carbon thin film deposition. The invention also provides methods of controlling physical properties of carbon thin films. In addition, the present invention provides methods of making carbon containing patterned structures. Further, the present invention provides methods of using carbon thin films and carbon containing patterned structures in NEMS, MEMS and other devices. More particularly, the invention provides a method and apparatus for sensing electromagnetic radiation in the infrared spectrum using a bolometer device. The invention also provides a method and apparatus for sensing chemical species. But it would be recognized that the invention has a much broader range of applicability. For example, the invention can be applied to other wavelengths such as millimeter waves or visible light, biological materials, and other species and/or particles, and the like.
As technology progresses, certain types of detection devices have become important. Detection devices range from motion sensors to those that detect certain frequencies of electromagnetic radiation and detectors for a variety of chemical species. Motion sensors include, among others, mechanical, capacitive, inductive, and optical designs. A specific type of motion sensor includes accelerometers and the like, which rely upon MEMS based technology. Such detection devices also include, among others, infrared detectors, and imagers. An example of an infrared detector is a bolometer. Other types of detectors include chemical sensors, which rely upon sensing differences in voltage potentials while being coupled to an unknown chemical species.
Although many of these sensor designs have had certain success, a variety of drawbacks or limitations still exist. For example, conventional bolometer designs are often difficult to manufacture cost efficiently due to constraints in materials and processing techniques. Additionally, many if not all of these sensor designs use conventional mechanical, capacitive, inductive, and optical techniques that rely upon a variety of conventional metals and/or semiconductor materials. Such materials are often limited in the ability to provide an efficient and highly accurate device. Such materials are often reactive and may degrade over expended periods of time. These and other limitations of conventional devices can be found throughout the present specification and more particularly below.
From the above, it is seen that an improved technique for manufacturing devices is highly desired.